What is Feline Hyperthyroidism?

Hyperthyroidism is a common condition typically affecting older cats . It is caused when the thyroid gland, found in the neck, produces excessive amounts of the hormone thyroxine. The usual cause for increased hormone is a tumor on the thyroid gland which may be benign (non-cancerous) or malignant (cancerous).
Thyroxine controls the speed of your cats metabolism, and when high will often cause a range of clinical signs relatively obvious to the owner.
Thyroxine also helps to control blood pressure, heart rate and gastrointestinal function.
 

How is Hyperthyroidism Diagnosed?
Hyperthyroidism is diagnosed through a blood test that checks the level of thyroxine in your cats blood. Initially other blood tests may be done to check there is no other underlying disease. A higher than normal blood thyroxine level will indicate hyperthyroidism and a treatment plan established and started.

How is Hyperthyroidism managed?
Once diagnosed, your cat will need to have regular vet checks and blood testing to make sure the thyroxine levels return to the “normal” range and that the treatment plan is working. Often this will mean follow up blood testing 4-6 weeks from the start of treatment, and depending on results every 3-6 months ongoing. Once the hyperthyroidism is well controlled monitoring in the form of a vet consultation and blood testing will be required at least every 6 months to ensure the treatment is working as it should.

What are the clinical signs?
Hyperthyroidism can range in severity, with the most common symptom being an increased appetite related to the increased metabolism. Other signs may include; increased thirst, weight loss even with an increased appetite, hyperactivity, dairrhoea and/or vomiting, poor skin and coat condition and increased heart rate.
 

What are the treatment options?
Thankfully hyperthyroidism can be well managed, and even cured due to many different treatment options. The one we commonly recommend is radioactive iodine, you can read about this below.

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What is Radioactive Iodine?
Radioactive iodine treatment, more commonly known as I131 treatment, is when a natural form of iodine that is radioactive is used to treat cats suffering from hyperthyroidism When the radioactive dose of iodine is administered the thyroid gland concentrates this which therefore destroys the overactive cells in the thyroid gland. This brings the thyroid gland back to its normal function.
 

Is Radioactive Iodine safe?
Radioactive iodine is safe for both your cat and your family. The dose given is very low and the radioactivity is concentrated in the problem area. Even though it is a low dose, cats are kept in a special boarding facility for 7 days to be 100% safe.

 

After 21 days the radiation levels are negligible because the radioactive iodine disappears very quickly. 95% of cats respond to one dose of I131 and have normal thyroid hormone levels one month later. Around 5% of cats will need a second dose of radioactive iodine. Rarely radioiodine treatment can reduce the thyroid gland too much, meaning the cat doesn’t produce enough thyroid hormone. Generally this will last 4-6 weeks and happens in approximately 2% of cases. Studies have shown that once cured, the disease will recur in only 2% of cats in the following 6 year period after receiving radioactive iodine treatment.
 

Why use I131
Other methods of treating hyperthyroidism in cats can be time consuming and hard to manage.
These include;

   - Daily life-long pilling or topical gel application to the inside of the ear.
   - Prescription diet only feeding, hard to manage and only useful for indoor cats.
Radioactive iodine is a one off injection, relatively painless and highly effective at curing hyperthyroidism—around 95% of cats are cured after one treatment. Because of this radioactive iodine is also a very cost effective treatment.

What is the treatment process?
For this treatment your cat will be admitted to the boarding facility and carefully examined. A small patch of fur over the shoulder will be clipped for the iodine injection, which is then administered by the veterinarian. After the injection your cat will stay in the boarding facility for 7 days

When will my cat come home?
Your cat can leave our boarding facility after 7 days. When you take your cat home after 7 days there are some guidelines you’ll need to follow which will be discussed with you at the time of booking.
 

Further information
For any further information about radio-active iodine treatment please consult with your veterinarian. Before treatment takes place your cat will undergo a few important blood and urine tests which is a good time to discuss any questions with your vet.